Containment system and a method for using said containment system

ABSTRACT

A containment system for recovering hydrocarbon fluid from a leaking device comprising a dome sealed to the seafloor around the leaking device and forming a cavity for accumulating hydrocarbon fluid. The dome comprises an upper output opening for extracting the hydrocarbon fluid, and an over pressure valve for extracting fluid out from the cavity to the environment if pressure inside the cavity is too high.

RELATED APPLICATIONS

The present application is a National Phase entry of PCT Application No. PCT/EP2012/075676, filed Dec. 14, 2012, which claims priority from U.S. Patent Application No. 61/710,333, filed Oct. 5, 2012, said applications being hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention concerns a containment system for recovering spilled oil that is leaking under water.

BACKGROUND OF THE INVENTION

The present invention concerns more precisely a containment system for recovering a hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking the hydrocarbon fluid from a well.

Recovering oil that is leaking from an under water oil device is a great problem, especially for oil device that are installed at deep sea floor.

The explosion on the “Deepwater Horizon” platform in the Gulf of Mexico demonstrated how much such a containment system is difficult to control.

One of the main problems was the formation of hydrates that clogged the used containment system.

For example, at a depth of around 1500 meters, the sea water is cold (for example around only 5° C.) and at a high pressure. These environment conditions may transform the sea water and hydrocarbon fluid into hydrates having a quasi-solid phase and which can fill and clogged any cavity.

Hydrates inhibitors like methanol could be injected to avoid hydrate formation. But, the needed quantity of such chemical is huge and inhibitors are also pollution for the environment.

OBJECTS AND SUMMARY OF THE INVENTION

One object of the present invention is to provide a containment system that avoids the formation of hydrates inside the dome.

To this effect, the containment system of present invention is adapted to be landed at the seafloor corresponding to a base level of the containment system. It comprises a dome intended to be sealed to the seafloor around the leaking device and forming a cavity under said dome, said cavity being adapted to completely surround and include the leaking device, and to accumulate hydrocarbon fluid coming upwardly from the leaking device, said dome comprising at least one upper output opening adapted to extract the hydrocarbon fluid for recovering.

The dome further comprises an over pressure valve that extract fluid out from the cavity to the environment if a pressure difference between the cavity and the environment exceeds a predetermined pressure limit.

Thanks to these features, the fluids contained inside the dome volume around the leaking device is heated by the hydrocarbon fluid outputting from the leaking device, and is not cooled by the sea water.

The dome is substantially sealed, and the leaking device can not suck cold sea water from the environment.

The pressure inside the cavity is limited by the over pressure valve.

As the thermal exchanges between the sea water and the hydrocarbon fluid are cancelled and as the pressure inside the cavity can not increase above a predetermined value, the hydrates formation is prevented inside the cavity of the containment system of present invention.

In various embodiments of the containment system, one and/or other of the following features may optionally be incorporated.

According to an aspect of the containment system, the dome further comprises an injection device that inputs a warm fluid into the cavity.

According to an aspect of the containment system, the injection device comprises a plurality of output ports spread inside the cavity, said output ports being fed with the first warm fluid.

According to an aspect of the containment system, the containment system further comprises a pipe having an inner tube forming an inner channel, and an outer tube surrounding said inner tube and forming an annular channel, and wherein the inner channel is used to extract the hydrocarbon fluid from the upper output opening and the annular channel is used to feed the dome with at least a warm fluid, or inversely.

According to an aspect of the containment system, the dome comprises a material that is a thermally isolating material.

According to an aspect of the containment system, the thermally isolating material has a thermal conductivity lower than 0.1 W·m⁻¹·K⁻¹.

According to an aspect of the containment system, the containment system further comprises at least one sensor for measuring an interface level of a fluid interface between sea water and hydrocarbon fluid inside the dome, at least one output valve connected to the upper output opening for outputting hydrocarbon fluid from the cavity, and a control unit for controlling said interface level on the bases of the interface level measured by the sensor.

According to an aspect of the containment system, the dome comprises:

-   -   a first output opening for extracting a first phase from the         cavity, said first output opening being positioned on the dome         at a level proximal to the first level, said first phase being         for example an oil phase of the hydrocarbon fluid, and     -   a second output opening for extracting a second phase from the         cavity, said second output opening being positioned on the dome         at a level proximal to a highest level of the dome, said second         phase being lighter than the first phase, and being for example         a gas phase of the hydrocarbon fluid.

According to an aspect of the containment system, the over pressure valve is a ball check valve.

Another object of the invention is to provide a method for using a containment system for recovering hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking hydrocarbon fluid from a well. The containment system comprises at least:

-   -   a dome intended to be sealed to the seafloor around the leaking         device and forming a cavity under said dome, said cavity being         adapted to completely surround and include the leaking device,         and to accumulate hydrocarbon fluid coming upwardly from the         leaking device.

The dome comprises

-   -   at least one upper output opening adapted to extract hydrocarbon         fluid for recovering,     -   an over pressure valve adapted to extract fluid out from the         cavity to the environment if a pressure difference between the         cavity and the environment exceeds a predetermined pressure         limit, and     -   an injection device that injects a warm fluid into the cavity.

The method of the invention comprises the following successive steps:

a) injecting the warm fluid inside the cavity by the injection device and making the containment system to go down towards the leaking device,

b) installing the dome around the leaking device on the seafloor, so as the base level corresponds to the seafloor.

Thanks to the above method, the dome can be installed above the leaking device without hydrates formation inside the cavity.

In preferred embodiments of the method proposed by the invention, one and/or the other of the following features may optionally be incorporated.

According to an aspect of the method, after step b) the method comprises a step of sealing the dome to the seafloor.

According to an aspect of the method, after step b), the method comprises a step of stopping the injection of warm fluid if hydrates formation is not detected inside the cavity.

According to an aspect of the method, the containment system further comprises at least one sensor, at least one output valve connected to the upper output opening, and a control unit, and the method further comprises the following steps:

-   -   the at least one sensor measures an interface level of a fluid         interface between sea water and hydrocarbon fluid inside the         dome,     -   the control unit calculates a control value of the at least one         output valve on the bases of said measured interface level, and         controls said at least one output valve for outputting         hydrocarbon fluid from the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the following detailed description of at least one of its embodiments given by way of non-limiting example, with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic view of a vertical cut of a containment system according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the various figures, the same reference numbers indicate identical or similar elements. The direction Z is a vertical direction. A direction X or Y is a horizontal or lateral direction. These are indications for the understanding of the invention.

As shown on FIG. 1, the containment system 1 of present invention is adapted for recovering hydrocarbon fluid from a leaking device 2 that is situated at a seafloor 5 of a deep offshore installation. The leaking device 2 is for example the well itself, a pipeline, a blow out preventer device, a wellhead or any device connected to the wellhead. The seafloor 5 is for example at more than 1500 meters deep below the sea surface 4. At this depth, the sea water is cold, for example around only 5° C. and at high pressure.

The hydrocarbon fluid may be liquid oil, natural gas, or a mix of them.

The leaking device 2 is leaking a hydrocarbon fluid from an subsea well 3. The hydrocarbon fluid exiting from the subsea may be rather hot, for example above 50° C. However, the environment cold temperature and high pressure may transform the sea water and hydrocarbon fluid into hydrates having a quasi-solid or solid phase. These hydrates can fill and clogged any cavity.

The containment system 1 of present invention is landed and fixed to the seafloor by any means, such as anchoring or heavy weights 29 for compensating the upward Archimedes force applied on the containment system 1 by the hydrocarbon fluid that is lighter than the sea water (lower mass density). The seafloor corresponds in the present description to a base level of the containment system 1. The other levels are defined going upwards, in the vertical direction Z towards the sea surface 4.

The containment system 1 of present invention comprises at least:

-   -   a dome 20 intended to be sealed on the seafloor and forming a         cavity 21 under said dome 20, said cavity accumulating the         hydrocarbon fluid,     -   an upper output opening 22 to extract the hydrocarbon fluid for         recovering, and     -   an over pressure valve 23 to extract fluid from the cavity to         the environment if a pressure difference between the cavity and         the environment exceeds a pressure limit.

The dome 20 is preferably fixed to the seafloor.

For example, the dome 20 comprises foot 20 c having heavy weights for sealing and securing the dome 20 to the seafloor.

The dome 20 completely surrounds the leaking device 2. In a horizontal plane (XY), the dome 20 has a closed loop shape encompassing the leaking device 2. Said shape may be for example a circle shape, a square shape or any polygonal shape.

The dome 20 has an diameter D20. This outer diameter corresponds to a maximum distance between two internal points of the dome, taken in an horizontal plane at a level near the base level BL. The diameter D20 is for example of 6 meters or more.

The dome 20 is higher than a total height of the leaking device 2. It has a height H20 of approximately 3 meters or more. It completely includes the leaking device 2 (i.e. the part above the base level. All that is under the seafloor is not taken into account as the dome is sealed to the seafloor).

The dome 20 defines an inner dome volume, called the cavity 21. This volume is isolated (not in communication) with the environment sea water. The thermal exchange between the cold sea water and the hydrocarbon fluid is cancelled. This first effect cancels the hydrate formation.

The dome 20 is a hollow structure having:

-   -   an upper portion 24 extending in a radial direction to an outer         peripheral end 24 a, said radial direction being perpendicular         to the vertical direction AX (equal to direction Z on the         figure), and     -   a lateral portion 25 extending from the upper portion 24         downwardly between an upper end 25 a and a lower end 25 b, said         lower end 25 b comprising for example the foot 20 c.

The lateral portion 25 has said diameter D20.

The lateral portion 25 of the dome is downwardly opened so as to surround the leaking device 2.

The dome 20 comprises an upper output opening 22 having of small diameter compared to the dome diameter. Said upper output opening is adapted to be connected to a pipe 50 for extracting the hydrocarbon fluid from the containment system 1 to a recovery boat 6 at the sea surface 4, so as the hydrocarbon fluid is recovered.

In a vertical plane (XZ), the upper portion 24 of the dome 20 may have a convergent shape from the lateral portion 25 up to the upper output opening 22. The dome 20 is a cover that can have advantageously an inverted funnel shape.

The hollow structure of the dome 20 forms a largely opened cavity 21 in the direction to the seafloor. It is positioned above and around the leaking device 2 so as to accumulate the light hydrocarbon fluid.

The cavity 21 accumulates hydrocarbon fluid coming upwardly from the leaking device 2, i.e. oil and/or natural gas. The hydrocarbon fluid fills the upper volume of the cavity, down to an interface level IL.

The containment system 1 advantageously comprises at least one sensor 60 for measuring the interface level IL of the fluid interface between sea water and the hydrocarbon fluid inside the dome 20.

The sensor 60 may give a first measurement of a liquid level corresponding to the interface level IL between the liquid component of the hydrocarbon fluid (e.g. oil) and the sea water, and a second measurement of a gas level corresponding to an interface between the liquid component and a gas component (e.g. natural gas) of the hydrocarbon fluid.

The containment system 1 additionally comprise an output valve 62 connected to the upper output opening 22 and/or pipe 50 for outputting the recovered hydrocarbon fluid to the recovery boat 6.

Then, a control unit 61 calculates a control value on the bases of a measured value of the interface level IL, and operates the output valve on the bases of the control value for outputting hydrocarbon fluid from the cavity. The control unit 61 may calculate the control value to keep the interface level at a constant level inside the cavity 21.

The containment system 1 may also comprise an injection device 30 that injects a warm fluid WF into the cavity 21. Therefore, the hydrocarbon fluid can be heated, and prevented to form hydrates.

The injection device 30 may comprise a plurality of output ports spread inside the volume of the cavity, so as to ensure a constant warming of the hydrocarbon fluid inside the cavity 21.

The injection device 30 may inject warm fluid WF from the upper portion 24, the lateral portion 25 or from both portions 24, 25 of the dome 20.

The warm fluid WF may be sea water pumped near the sea surface 4 via a pump 63.

The pumped sea water may be used as it, i.e. at the temperature of sea water at the sea surface 4, or heated by additional means.

The warm fluid may be water, oil, gas oil, or crude oil or any heat transfer fluid. The warm fluid may be additionally heated or not.

The pipe 50 is advantageously a two concentric tubes pipe, having an inner pipe 51 forming an inner channel, and an outer tube 52 surrounding said inner pipe 51 and forming an annular channel between the inner tube and the outer tube. The inner channel may be connected to the upper output opening 22 and used to extract the hydrocarbon fluid from the cavity 21. The annular channel may be therefore connected to the injection system 30, and used to feed it with the warm fluid from the surface. However, it is apparent that the two channel of such pipe can be connected to the dome according to the other inverse possibility without any change.

The containment system 1 may comprise other output openings and/or pipes for feeding additionally fluids, or for extracting other fluids, liquid or gases from the cavity.

For example, the containment system 1 may comprise a drain valve for purging or limiting the quantity of water inside the cavity 21. Said drain valve might be positioned proximal to the base level BL (seafloor).

Advantageously, the cavity 21 can be used as a phase separator for separating the water and the hydrocarbon fluid, and for separating each phase of the hydrocarbon fluid (oil, gas) so as to extract them separately.

To this end, the dome 20 may comprise:

-   -   a first output opening for extracting a first phase from the         cavity, said first output opening being positioned on the dome         at a level proximal to the first level L1, said first phase         being for example an oil phase of the hydrocarbon fluid, and     -   a second output opening for extracting a second phase from the         cavity, said second output opening being positioned on the dome         at a level proximal to a highest level of the dome, said second         phase being lighter than the first phase, and being for example         a gas phase of the hydrocarbon fluid.

Thanks to the above first and second output opening, quantities of each phase (oil, gas) can be limited inside the cavity 21 to predetermined values. An Archimedes force maximum that applies on the containment system 1 can be predetermined, and the weights of the foot 20 c can therefore be predetermined for maintaining the containment system 1 landed at the seafloor 5.

The upper portion 24 of the dome 20 may comprise output openings, called vents, for evacuating large quantities of fluid inside the cavity 21. These vents are helpful to facilitate the installation of the containment system 1 above the leaking device 2. The vents are opened during the first transient steps of installation, noticeably when the containment system 1 is made to go down to the seafloor 5 around the leaking device 2. During these steps all the hydrocarbon fluid may be evacuated to cancel its Archimedes force on the containment system and to prevent hydrates formation problem.

Moreover, the dome 20 may comprises upper and lateral portions 24, 25 that comprise thermal isolating material, so as to thermally isolate the cavity 21 from the cold environment of sea water. Ideally, the dome 20 may be manufactured with at least a thermally isolating material, said thermally isolating material preferably having a thermal conductivity lower than 0.1 W·m⁻¹·K⁻¹.

The following thermal isolation materials may be used: synthetic material such as Polyurethane (PU) or polystyrene material, or a fibre textile with Polyvinyl chloride (PVC) coating or PU coating, or Alcryn @. The thermal isolation material may be foam, or a gel contained inside a double wall structure.

The dome 20 may comprise a plurality of walls, layers or envelopes for improving the thermal isolation. Between the layers, isolation materials may be included, or heating devices (electric, hydraulic or of any kind) to improve again the thermal isolation of the dome.

The thermal isolation of the dome 20 passively isolates the cavity 21, while the first injection device 30 actively isolates the cavity 21. Both effects prevent the formation of hydrates inside the cavity 21.

The cavity 21 is a volume storing a quantity of hydrocarbon fluid and absorbing the fluctuations of hydrocarbon fluid flows.

The dome 20 comprises an over pressure valve 23 that extract fluid out of the cavity and into the environment if a pressure difference between the cavity 21 and the environment exceeds a predetermined pressure limit.

The predetermined pressure limit is for example of 10 bars, 20 bars, or 50 bars. This limit has to be determined accordingly with the cavity size and the leaking device flow.

The over pressure valve is for example a ball check valve. The ball check valve comprises a support element, a ball, and a spring that loads the ball to the support element so as to close an opening. The tuning of the spring load is adapted to the predetermined pressure limit.

Advantageously, the dome 20 of present embodiment is fed with warm fluid before and during the sealing and fixing step of the dome 20 above the seafloor, so as hydrates formation is prevented.

The cavity 21 is closed, and the fluid inside the cavity is rapidly heated by the hydrocarbon fluid itself outputting from the leaking device 2.

The over pressure valve 23 insures that the pressure inside the cavity is not increasing, and then insuring that the containment system is not destroyed.

The predetermined pressure limit may insure that hydrates formation is prevented.

The method for using or installing the containment system 1 according to the invention is now explained.

The dome of the containment system 1 comprises:

-   -   at least one upper output opening 22 adapted to extract the         hydrocarbon fluid for recovering,     -   an over pressure valve 23 adapted to extract fluid out from the         cavity to the environment if a pressure difference between the         cavity and the environment exceeds a predetermined pressure         limit, and     -   an injection device 30 that injects a warm fluid into the         cavity.

The method comprises the following successive steps:

a) injecting the warm fluid inside the cavity 21 by the injection device 30 and making the containment system to go down towards the leaking device 2,

b) installing the dome 20 around the leaking device 2 on the seafloor, so as the base level corresponds to the seafloor 5.

Thanks to the above method, the volume of the cavity 21 is continuously heated before the dome is installed above the leaking device 2. After installation, the volume of the cavity 21 is heated by the warm fluid and by the hydrocarbon fluid itself.

The fluids inside the cavity 21 are then continuously heated, and the hydrates formation is prevented.

Then, the dome 20 can be sealed to the seafloor 5 by any means.

Then if the hydraulic and thermal conditions are steady inside the cavity 21 around the leaking device 2, the injection of warm fluid by the injection device 30 can be stopped. The fluid inside the cavity will be heated only by the hydrocarbon fluid exiting from the leaking device 2.

If the flow of hydrocarbon fluid is fluctuating, and if the pressure inside the cavity 21 is increasing too much, the over pressure valve 23 will open to limit the pressure.

Thanks to the above pressure limitation, hydrates are also prevented.

The containment system 1 may also further comprises a sensor 60, an output valve 62 connected to the upper output opening 22, and a control unit 61.

The sensor measures an interface level IL of a fluid interface between sea water and hydrocarbon fluid inside the dome 20. The control unit calculates a control value of the at least one output valve on the bases of said measured interface level, and it controls the output valve for outputting hydrocarbon fluid from the cavity 21.

Thanks to the above method, hydrocarbon fluid can be efficiently recovered from the leaking device 2, even at a great depth, and without hydrates formation.

The embodiments above are intended to be illustrative and not limiting. Additional embodiments may be within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Various modifications to the invention may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant art will recognize that the various features described for the different embodiments of the invention can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations, within the spirit of the invention. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the invention. Therefore, the above is not contemplated to limit the scope of the present invention. 

1. A containment system for recovering hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking hydrocarbon fluid from a well, wherein the containment system is adapted to be landed at the seafloor corresponding to a base level of the containment system, and wherein the containment system comprises a dome intended to be sealed to the seafloor around the leaking device and forming a cavity under said dome, said cavity being adapted to completely surround and include the leaking device, and to accumulate hydrocarbon fluid coming upwardly from the leaking device, said dome comprising at least one upper output opening adapted to extract the hydrocarbon fluid for recovering, and wherein the containment system is characterised in that the dome further comprises an over pressure valve to extract fluid out from the cavity to the environment if a pressure difference between the cavity and the environment exceeds a predetermined pressure limit.
 2. The containment system according to claim 1, wherein the dome further comprises an injection device that inputs a warm fluid into the cavity.
 3. The containment system according to claim 2, wherein the injection device comprises a plurality of output ports spread inside the cavity, said output ports being fed with the first warm fluid.
 4. The containment system according to claim 2, further comprising a pipe having an inner tube forming an inner channel, and an outer tube surrounding said inner tube and forming an annular channel, and wherein the inner channel is used to extract the hydrocarbon fluid from the upper output opening and the annular channel is used to feed the dome with at least a warm fluid, or inversely.
 5. The containment system according to claim 1, wherein the dome comprises a material that is a thermally isolating material.
 6. The containment system according to claim 5, wherein the thermally isolating material has a thermal conductivity lower than 0.1 W·m⁻¹·K⁻¹.
 7. The containment system according to claim 1, further comprising at least one sensor for measuring an interface level of a fluid interface between sea water and hydrocarbon fluid inside the dome, at least one output valve connected to the upper output opening for outputting hydrocarbon fluid from the cavity, and a control unit for controlling said interface level on the bases of the interface level measured by the sensor.
 8. The containment system according to claim 1, wherein the dome comprises: a first output opening for extracting a first phase from the cavity, said first output opening being positioned on the dome at a level proximal to the first level, said first phase being for example an oil phase of the hydrocarbon fluid, and a second output opening for extracting a second phase from the cavity, said second output opening being positioned on the dome at a level proximal to a highest level of the dome, said second phase being lighter than the first phase, and being for example a gas phase of the hydrocarbon fluid.
 9. The containment system according to claim 1, wherein the over pressure valve is a ball check valve.
 10. A method for using the containment system for recovering hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking hydrocarbon fluid from a well, and wherein the containment system comprises at least a dome intended to be sealed to the seafloor around the leaking device and forming a cavity under said dome, said cavity being adapted to completely surround and include the leaking device, and to accumulate hydrocarbon fluid coming upwardly from the leaking device, and wherein said dome comprises: at least one upper output opening adapted to extract the hydrocarbon fluid for recovering, an over pressure valve adapted to extract fluid out from the cavity to the environment if a pressure difference between the cavity and the environment exceeds a predetermined pressure limit, and an injection device that injects a warm fluid into the cavity, and wherein the method comprises the following successive steps: a) injecting the warm fluid inside the cavity by the injection device and making the containment system to go down towards the leaking device, b) installing the dome around the leaking device on the seafloor, so as the base level corresponds to the seafloor.
 11. The method according to claim 10, wherein after step b) the method comprises a step of sealing the dome to the seafloor.
 12. The method according to claim 10, wherein after step b), the method comprises a step of stopping the injection of warm fluid if hydrates formation is not detected inside the cavity.
 13. The method according to claim 10, wherein the containment system further comprises at least one sensor, at least one output valve connected to the upper output opening, and a control unit, and wherein the method further comprises the following steps: the at least one sensor measures an interface level of a fluid interface between sea water and hydrocarbon fluid inside the dome, the control unit calculates a control value of the at least one output valve on the bases of said measured interface level, and controls said at least one output valve for outputting hydrocarbon fluid from the cavity.
 14. The method according to claim 11, wherein after step b), the method comprises a step of stopping the injection of warm fluid if hydrates formation is not detected inside the cavity. 